A pull-type harvesting machine is provided having a hydraulically controlled header tilt adjustment mechanism that can be operated from the tractor seat of a towing vehicle. The tilt adjustment mechanism includes a hydraulic tilt circuit and a remotely operated control valve assembly connectable with the tilt circuit and another operating circuit of the harvester. The valve assembly is shiftable between a pair of alternative positions for communicating either the operating circuit or the tilt circuit with the towing vehicle's source of hydraulic pressure. Accordingly, a single source of pressurized fluid may be controlled from within the towing vehicle to alternatively operate either the header tilt mechanism or another function of the harvester, such as swinging of a pulling tongue from side-to-side for lateral positioning of the machine relative to a towing vehicle.